The requirements on splicing technology of display screen and display device are progressively stricter as the increasingly wider application of Compact TV (i.e., narrow bezel TV) and Public Information Display (PID) splicing screen which are popular in recent years. A splicing screen is a large-framed screen constituted by a plurality of display screens which are arranged, as display units, in a matrix (e.g., 2×2, 3×3, 4×4 or even larger one based on freely unlimited splicing) for displaying a large-sized image with each display screen displaying a portion of the image or for respectively displaying different images on different display screens.
Input signals of a splicing screen are allocated to each of the display screens after completely processed by an image controller. The image displayed on each display screen can extend beyond a border of the display screen, which, however, usually needs to ensure a minimum gap between display screens. The display quality of an individual display screen will directly influence the display effect of the whole splicing screen which significantly varies depending on the type of the utilized display screen. An image processor, as one of the core devices of a splicing screen, serves for sending signals of computer, video and network to be displayed to an image splicing controller; the processed image signals are sent to corresponding display screens, respectively, with each display screen only displaying a portion of the entire image, so that a complete, large display frame can be established by combining all the portions on the display screens together. The resolution of the large display frame is a multiple of that of each display screens. However, the image processor can only make improvement in video processing, and the splicing effect presented by the splicing screen as obtained still involves a considerable wide splicing gap and can not meet the requirement of narrow splicing gap. As shown in FIG. 1, an example of a 2×2 splicing screen is illustrated, in which each display screen displays a small image.
The technology of narrow bezel splicing screen in conventional technology is to narrow the bezel width of each display screen to achieve an objective of narrowing the splicing gap between the spliced screens after completion of splicing. FIG. 2 is a schematic view showing the design of alignment marks disposed around the narrow bezel splicing screen according to a conventional technique. In the figure, A, B and C are representative of the upper left corner, lower left corner and lower right corner of a small display screen, respectively; 1A, 2A and 3A are representative of three alignment marks at the upper left corner; 1B, 2B and 3B are representative of three alignment marks at the lower left corner; 1C, 2C and 3C are representative of three alignment marks at the lower right corner. Each of the alignment marks has an exclusive area around it for excluding any image therein. The alignment mark has an area of 0.5 mm×0.5 mm, and its exclusive area has an area of 1.5 mm×1.5 mm. If there are other images extending into the scope of the exclusive area of the alignment mark, the production line will generate an alarm and fail to tape-out. As shown in FIG. 2, the three alignment marks at the upper left corner and their exclusive areas are not overlapped with each other, thus it will not result in a tape-out failure. However, the three alignment marks at the lower left corner, the three alignment marks at the lower right corner, and the respective exclusive areas of these alignment marks are overlapped one another, especially the exclusive areas of the alignment marks 1B, 2B and 3B at the lower left corner are considerably overlapped with each other. As shown in the enlarged view of FIG. 3, the lower left corner of the exclusive area of alignment mark 2B is partially overlapped with the alignment mark 1B, and the upper right corner of the exclusive area of alignment mark 2B is partially overlapped with the exclusive area of alignment mark 3B, resulting in that some of the images are extending into the exclusive areas of alignment marks, which leads to a tape-out failure.
For achieving a narrow bezel of a splicing screen, the existing process allowance has to be reduced to the minimum, so as to reduce the width of the display screen at the alignment mark and the width of the alignment mark on the substrate, so as to improve accuracy and standard. However, merely relying on reducing the existing process allowance contributes little to the narrowing of the bezel of splicing screen, and problems that influence the display effect of the splicing screen remains unsolved.